This invention relates generally to methods and devices used for forming elongate wire, rod, tubing and the like into shapes, in particular forming wire or tubing into helical shapes.
As disclosed in WO 2013/158916 the contents of which are incorporated herein by reference, a heat exchanger in which the heat exchanger tubes are formed into helical tube bundles has significant advantages over straight-tube heat exchangers in terms of durability, size and thermal efficiency.
Apparatus and methods for forming a single rod of wire or tube into a helical shape are well known. U.S. Pat. No. 4,402,205 to Yakovlev et al. discloses various methods for forming helical springs by winding a resilient rod around a rotating mandrel. U.S. Pat. No. 4,606,209 to Eisinger discloses a disk roller mechanism for forming a wire into a helical shape in which the wire is drawn through a plurality of staggered disk-shaped forming rollers while the wire is also being rotated about its own axis. Although the prior art discloses numerous methods of forming a single wire into a helix, or multiple thin strands into wire rope, the prior art does not disclose a method and apparatus for simultaneously forming a plurality of tubes or rigid rods into a helical bundle.